1. Field of the Invention
The present invention relates to an optical fiber part that includes an optical fiber having a taper fiber portion and a laser processing machine that includes the optical fiber part.
2. Description of the Related Art
Conventionally, laser processing machines have been used in various fields, such as printing and processing. Further, in recent years, high-output semiconductor lasers were realized, and optical fiber parts that transmit, through optical fibers, high-output laser light that has been output from the high-output semiconductor lasers, and output the high-output laser light are known. Further, as described in Japanese Unexamined Patent Publication No. 2003-248141, when the optical fiber parts are used, the ends (leading ends) of the optical fibers are attached and fixed into V-shaped grooves or the like in many cases. Further, use of such optical fiber parts in laser processing machines is being studied.
Further, an optical fiber that has a taper fiber portion at the leading end thereof is well known. The taper fiber portion has a core having a core diameter that decreases along an optical axis so as to output light that has a small beam diameter. For example, a taper fiber portion (taper fiber) that has a core having a core diameter decreasing from 105 μm to 60 μm and a cladding having an outer diameter thereof decreasing from 125 μm to 80 μm may be formed at the leading end of a main fiber in the following manner. A main fiber that has a core diameter of 105 μm and an outer diameter of the fiber of 125 μm is heated and stretched at the leading end thereof, and cut at a certain position, thereby forming the taper fiber.
Normally, when the NA (numerical aperture) (divergence angle) of a taper fiber (T) is NA(T), and the NA of a main fiber (main), which is a parent material (base material), is NA(main), and the core diameter of the taper fiber on the light incident side (input side) is Din, and the core diameter of the taper fiber on the light output side is Dout, the following equation is satisfied:NA(T)=NA(main)÷(Din/Dout).
When this equation is applied to the aforementioned example,NA(T)=NA(main)÷(105/60)=0.57 NA(main).
Therefore, light that has propagated through the main fiber and entered the taper fiber at an angle greater than 0.57 NA(main) cannot propagate through the taper fiber, and is radiated (output) to the outside of the fiber through the cladding.
For example, when the taper fiber is attached and fixed into a V-shaped groove, as described in Japanese Unexamined Patent Publication No. 2003-248141, and especially when an epoxy-based adhesive or the like that has low heat conductivity is used to attach and fix the taper fiber, the light output through the cladding of the taper fiber is absorbed by the epoxy-based adhesive. Consequently, the temperature of the adhesive increases, and there is a risk that the quality of the adhesive changes and deteriorates.